Combining Cu7S4 ultrathin nanosheets and nanotubes for efficient and selective absorption of anionic dyes

The growth of unique two-dimensional nanosheets on hollow and porous metal sulfides has received significant attention in adsorption and catalysis applications. Herein, we report a facile strategy to grow ultrathin nanosheets (NSs) on Cu7S4 nanotubes (NTs) via a two-step process (Cu7S4-NS-T). First, the obtained Cu nanowires (NWs) are oxidized in a hydrogen peroxide solution to form Cu@CuO composite nanowires decorated with ultrathin CuO NSs. Then, Cu7S4-NS-T composed of Cu7S4 NTs and Cu7S4 NSs is obtained from Cu@CuO NWs via a sulfurization process with the Kirkendall effect, in which anion-exchange reaction between Cu@CuO and S2‐− anions resulted in the formation of hollow structure. Due to fuse porous nanotubes and ultrathin nanosheets with abundant exposed copper centers, the obtained Cu7S4-NS-T shows extraordinary adsorption ability for the removal of anionic dyes, such as Congo red (CR) with a maximum adsorption capacity of 1166.07 mg/g, much superior to that of commercial activated carbon. Adsorption equilibrium and kinetic studies indicate that chemisorption is the main control process for the enrichment of the anionic dyes. The Cu7S4-NS-T can be used as a novel effective adsorbent for rapidly and efficiently removing dyes contaminants in water.